The normal surface of the skin has a multiplicity of microorganisms on it. As long as the skin surface is intact, the microorganisms generally present no problem to the body, achieving some natural balance with each other. When a surgical procedure is conducted which breaches the natural barrier formed by the skin, it is important that these normally present microorganisms be prevented from entering the wound. Various protocols to reduce or eliminate skin microorganisms have been developed and are generally practiced rigorously. The protocols generally involve a thorough scrubbing of the skin surface with an antimicrobial agent, possibly shaving the area if hair is present, and draping the patient with sterile drapes so that only the immediate area of the procedure is exposed. Following the procedure, the wound area is covered with a dressing for isolation until healing is substantially complete.
These procedures are generally successful, with the occurrence of post-surgical infections being maintained at a low level in most institutions. The goal of all these practices is to rapidly decrease the microbial count present on the skin, then prevent regrowth of the organisms during the period when the surgical site is open and during the subsequent healing process.
Many of the common protocols require scrubbing the surgical site with isopropyl alcohol for a prescribed time or scrubbing the site with an iodophor such as polyvinylpyrrolidone iodine or other antimicrobial agent. The area is then draped with sterile drapes leaving only the actual surgical field area exposed. During the procedure, the freshly scrubbed site may be subjected to blood, various body fluids and saline washes coupled with mechanical abrasion by sponges and the like. The effect of these washes may be to remove any residual antimicrobial agent, reinfect the surface and allow a regrowth of microorganisms that potentially may enter the open wound. Several workers have addressed the problem of surgical site preparation by incorporation of an antimicrobial agent into a material that forms a film when applied to skin surface. Cardelli et al. U.S. Pat. No. 4,374,126 teaches a composition and method for forming a film from an alcohol soluble carboxylated polyacrylate which includes an antimicrobial agent, an adhesion promoter and a difunctional amide for crosslinking the polymer as the alcohol solvent evaporates. The film formed is thus resistant to body fluids, can remain on the skin for up to two days providing both initial and sustained anti-microbial activity.
Dell U.S. Pat. No. 4,542,012 teaches a film forming polymer containing complexed iodine as a broad spectrum antimicrobial agent. The composition is applied to the skin from a volatile solvent, which when evaporated, leaves the iodine containing polymer film. The iodine is released from the film to provide antimicrobial action.
Brink U.S. Pat. No. 5,173,291 teaches an iodine containing aqueous polymer emulsion which forms a film when applied to the skin surface. The film releases the iodine as an antimicrobial agent.
These cited examples provide improvements to surgical site preparation procedures. However, unless iodine is used as the antimicrobial agent, it is often difficult to visualize the area to which the film has been applied. Iodine, while effective as an antimicrobial agent, may cause tissue reactions and staining. Additionally, in many of the film forming agents available, it is difficult to visually determine when the application solvent has sufficiently evaporated to begin the procedure. Often a practitioner will physically touch the surface to see if it is dry. If the surface is not dry, such a touch may initiate a breach in the film which may provide a pathway for microorganisms. Thus there is a need for a composition for preparation of a surgical site by forming a film containing an antimicrobial agent which provides visual indication of the area to which the composition has been applied. If the composition also provided an indication when the delivery solvent was substantially eliminated, the practice of surgical site preparation would be further advanced.